The continuous rise of atmospheric carbon dioxide (CO₂) emissions highlights the urgent need for sustainable air purification technologies. Current Direct Air Capture (DAC) filters often rely on toxic amines, which limit long-term stability and safe application. Here, we report a non-toxic PAN-based nanofiber air filter fabricated by electrospinning and urea-assisted carbonization. Structural analyses confirmed the introduction of nitrogen functionalities that enhanced CO₂ affinity, while SEM and FT-IR revealed graphitic carbon formation. In air-chamber tests, the optimized carbonized nanofiber reduced CO₂ concentration from 25,000 ppm to 2,000 ppm, a level generally regarded as acceptable for indoor environments, while simultaneously removing over 95% of PM₁₀, PM_2.5, and PM_0.1 particulates. This dual functionality, combined with facile fabrication and material safety, demonstrates strong potential for PAN-derived carbon nanofiber membranes in DAC systems and eco-friendly air purification devices. These findings suggest a viable pathway toward scalable, sustainable air-filter technologies for carbon-neutral applications.